Injection molding molds typically comprise at least two mold parts which come together at a parting line to define a mold cavity into which the plastic is injected through appropriate orifices. After cooling, the mold parts are separated and the molded article ejected from the cavity. Complex shape articles typically require complex molds in the sense that many additional mold parts are required. Molded articles having undercut portions are a particular challenge to the mold designers as not only must additional mold parts be provided but usually means for moving those parts out of the way of the undercut must be provided to insure release of the molded article from the cavity. Hence the molds can become quite complex. Vanotti U.S. Pat. No. 4,209,160 and Reibold et al. U.S. Pat. No. 2,367,962, for example, illustrate molds where additional mold elements are provided to mechanically move or separate the cavity-forming mold parts to release a molded article having an undercut portion. Such additional mechanical elements unduly add to the complexity of the mold and often serve to limit or restrict the number of articles that could otherwise be molded in a single mold.
It is accordingly an object of the present invention to provide an injection molding mold for molding undercut articles which mold minimizes the number of individual mold parts needed to form the undercut-shaping portions of the mold cavity and to release the molded article therefrom. This and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.